Area Forecast Discussion
Issued by NWS Chicago, IL

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS63 KLOT 240709
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
209 AM CDT THU JUL 24 2014

.DISCUSSION...
207 AM CDT

TODAY THROUGH TONIGHT...
EARLY THIS MORNING SKIES ARE GENERALLY CLEAR...WITH ONLY A FEW
HIGH BASED CLOUDS. TEMPS HAVE BEEN ABLE TO RADIATE INTO THE LOW
50S...AND JUST BEFORE DAYBREAK A FEW POINTS COULD DIP TO THE UPR
40S.

BROAD ANTI-CYCLONIC FLOW WILL CONTINUE TO DOMINATE THE REGION
TODAY...PROVIDING ABUNDANT SUNSHINE AND UNSEASONABLY COOL/DRY AIR
FOR A SECOND DAY. TEMPS SHUD BE ABLE TO HOLD GENERALLY IN THE MID
70S...HOWEVER WITH A NORTHEAST FLOW OFF OF LAKE MICHIGAN THE COOLER
MARINE AIR MAY KEEP TEMPS ALONG THE SHORELINE IN THE UPR 60S.

BY THIS AFTN THE SFC RIDGE AXIS WILL BE DRIFTING EAST ACROSS THE
OHIO VALLEY...WITH FLOW SLOWLY TURNING SOUTHERLY BY LATE TONIGHT.
DEPENDING ON THE TIMING...TEMPS COULD RADIATE IN THE LATE EVENING
BEFORE HOLDING STEADY OVERNIGHT IN THE MID/UPR 50S. A WEAK WAVE WILL
BE SLIDING EAST FROM THE DAKOTAS LATE TONIGHT...WITH SOME ISENTROPIC
MOISTENING ON THE LEE-SIDE ALLOWING FOR SOME SPOTTY SHOWERS AND
PERHAPS AN ISO TSRA JUST BEFORE DAYBREAK FRI IN THE WESTERN CWFA.

CONFIDENCE THRU TODAY...HIGH.
CONFIDENCE IN PRECIP OVERNIGHT/TEMPS...MEDIUM.

FRIDAY THROUGH SUNDAY...
500MB RIDGE OVER THE SOUTHERN PLAINS WILL BEGIN TO
FLATTEN...ALLOWING A QUASI-ZONAL FLOW ALONG THE NORTHERN PERIPHERY
WITH A SERIES OF WEAK MID-LVL VORTS SLIDING EAST INTO THE UPPER
MIDWEST/GREAT LAKES. GUIDANCE HAS A WEAK SFC WAVE MOVING EAST FROM
THE CENTRAL PLAINS INTO THE GREAT LAKES FRI BEFORE WEAKENING. THE
STRONGER MID-LVL VORTICITY MAXIMA REMAINS CONFINED ALONG THE HIGH
PLAINS/CANADIAN PRAIRIES FRI/SAT...WHICH WILL ALLOW A FEW ROUNDS OF
SHOWERS/THUNDERSTORMS TO PUSH ACROSS THE FORECAST AREA STARTING
FRI-SUN. AT THIS TIME THOUGH IT DOES APPEAR THE BEST CHANCE FOR
PRECIP FRI WILL BE IN THE EVENING HOURS.

A BOUNDARY LAYS OUT OVER THE MID-MISSOURI VALLEY STRETCHING EAST
THRU OHIO SAT AFTN/EVE. FOR THE SECOND HALF OF THE WEEKEND THE
PATTERN WILL ONCE AGAIN BE STARTING TO CHANGE TOWARDS A WESTERN
RIDGE AND GREAT LAKES TROUGH. THE SEMI-STATIONARY MID-LVL VORT OVER
THE HIGH PLAINS WILL SLIDE EAST EARLY SUN INTO THE NORTHERN GREAT
LAKES...WITH A SERIES OF WEAK SFC WAVES CONSOLIDATING OVER LOWER
MICHIGAN SUN MORNING.

TEMPS WILL START TO MODERATE OVER THE WEEKEND INTO THE UPR 70S/LOW
80S...AND WITH THE INCREASED LLVL MOISTURE DEW PTS WILL CREEP BACK
INTO THE MID/UPR 60S SAT EVE. THE FAR WEST/SOUTHWEST FORECAST AREA
COULD SEE DEW PTS BACK INTO THE LOW 70S.

THEN FOR SUN A FRONTAL BOUNDARY WILL BE SLIDING SOUTHEAST ACROSS THE
CWFA...HOWEVER TEMPS SHUD STILL BE ABLE TO REACH 80 TO THE LOW 80S.

CONFIDENCE...MEDIUM/HIGH.

MONDAY THROUGH THURSDAY...
ENSEMBLES FOR SEVERAL CYCLES HAVE PROGGED A NORTH ATLANTIC RIDGE
COUPLED WITH A HIGH AMPLITUDE RIDGE DEVELOPING ACROSS WESTERN
CANADA. THE RESULTING FEATURE WILL LIKELY BE A TROUGH DIGGING SOUTH
ACROSS THE GREAT LAKES/HUDSON BAY EARLY NEXT WEEK AND LIKELY
PERSISTING THRU LATE NEXT WEEK. UNSEASONABLY COOL AIR WILL BLEED
SOUTH WITH ENSEMBLES DEMONSTRATING A HIGH CONFIDENCE IN THE 850MB
ISOTHERMS OVER THE FORECAST AREA GENERALLY BETWEEN 8-10 DEG C FOR
MON/TUE...THEN VERY SLOW TO MODERATE BACK TO A 10-12 DEG C RANGE
LATE WEEK. SO TO KICK-OFF NEXT WEEK TEMPS IN THE LOW 70S LOOK LIKELY
WITH A NORTHWEST FLOW AND BROAD SFC RIDGE. AS THE WEEK PROGRESSES
TEMPS SHUD PUSH BACK INTO THE MID/UPR 70S...BUT CURRENTLY THE
NORTHWEST FLOW WOULD SUGGEST DRY CONDITIONS TO PERSIST.

CONFIDENCE...HIGH.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* NONE.

BMD

//DISCUSSION...UPDATED 06Z...

WEATHER WILL REMAIN FAIRLY BENIGN OVER THE NEXT TAF PERIOD AS HIGH
PRESSURE BUILDS ACROSS THE REGION. NORTH WINDS TONIGHT WILL VEER
TO THE NORTHEAST MID MORNING THURSDAY WITH SPEEDS APPROACHING 10
KT THROUGH THE DAY. WINDS WILL CONTINUE TO VEER EVENTUALLY COMING
AROUND TO THE SOUTH THURSDAY EVENING AS THE RIDGE AXIS SLIDES EAST
OF THE AREA. VFR CONDITIONS ARE EXPECTED TO PREVAIL WITH
INCREASING HIGH THEN MID CLOUDS MAINLY LATE IN THE PERIOD.

BMD

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* HIGH.

BMD

//OUTLOOK FOR ORD/MDW FOR 12Z FRIDAY-12Z WEDNESDAY...UPDATED 00Z...

FRIDAY...CHANCE OF TSRA.

SATURDAY...CHANCE OF TSRA.

SUNDAY...CHANCE OF TSRA.

MONDAY...VFR.

TUESDAY...SLIGHT CHANCE OF SHRA LATE.

RODRIGUEZ

&&

.MARINE...
220 PM CDT

WINDS REMAIN IN THE 20 TO 25 KT ACROSS MUCH OF LAKE MICHIGAN EXCEPT
IN THE FAR NORTH BEHIND A STRONG COLD FRONT WHICH IS NOW WELL SOUTH
OF THE GREAT LAKES. SIGNIFICANT WAVE HEIGHTS PEAKED EARLIER TODAY
WITH 10 FT OBSERVED NEAR MICHIGAN CITY...AND WE ARE STILL SEEING 6
TO 8 FT WAVES ALONG THE SOUTHERN HALF OF THE LAKE WHERE RIP CURRENT
ACTIVITY HAS BEEN REPORTED ALONG THE INDIANA SHORELINE. A SMALL
CRAFT ADVISORY REMAINS IN EFFECT FOR THE INDIANA AND ILLINOIS
NEARSHORE WATERS DUE TO THE ELEVATED WINDS AND WAVES.

HIGH PRESSURE IS NOSING INTO THE UPPER MIDWEST...AND IT WILL
CONTINUE SLIDING SOUTH AND EAST ACROSS LAKE MICHIGAN TONIGHT ALLOWING
WINDS TO SUBSIDE OVERNIGHT INTO THURSDAY. WINDS WILL GENERALLY
REMAIN NORTHERLY OVER THE SOUTHERN HALF OF THE LAKE WITH ONSHORE
WINDS ON THE INDIANA AND ILLINOIS SHORES WHILE WINDS BEGIN TO TURN
SOUTHERLY ALONG THE NORTH HALF OF THE LAKE.  THE HIGH WILL DEPART TO
THE EAST AS LOW PRESSURE MOVES OUT OF THE NORTHERN ROCKIES INTO THE
PLAINS ON FRIDAY ALLOWING WINDS TO HAVE A SOUTHERLY COMPONENT ACROSS
THE LAKE.

THE NEXT ORGANIZED COLD FRONT WILL PASS THROUGH ON SUNDAY. THE
SURFACE LOW ASSOCIATED THIS FRONT WILL DEEPEN IN THE EASTERN LAKES
ON MONDAY WHILE HIGH PRESSURE AGAIN BUILDS SOUTH INTO THE UPPER
MIDWEST. THIS WILL CREATE A PERIOD OF GUSTY NORTHWEST TO NORTH WINDS
WHICH REACH 25 TO 30 KT.

KMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...BEACH HAZARDS STATEMENT...ILZ006-ILZ014 UNTIL 10 AM THURSDAY.

IN...BEACH HAZARDS STATEMENT...INZ001-INZ002 UNTIL 10 AM THURSDAY.

LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 10 AM THURSDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.